A bi-directional radio communication system includes a transmitter, a receiver, and an antenna. The transmitter can receive data carrying certain information and general electrical signals based on the data, and transmit the electrical signals to the antenna. The antenna can convert the electrical signals received from the transmitter into radio signals. The radio signals can propagate, in the form of radio waves, over a distance to transmit the information. The antenna can also receive radio signals and convert that into electrical signals, and provide the converted electrical signals to the receiver. The receiver can amplify and filter the electrical signals received from the antenna, and provide the electrical signals to other circuit blocks to extract information. The transmitter and the receiver can be integrated on an integrated circuit (IC) chip, whereas the antenna can be an off-chip component and not part of the IC chip.
In the communication system, the antenna can be coupled with the transmitter and the receiver via a fixed electrical connection. Each of the transmitter and the receiver can be individually controlled to access the antenna. For example, when the transmitter is transmitting electrical signals to the antenna via the fixed electrical connection, the receiver can be either disabled or controlled to discard the electrical signals from the transmitter. Also, when the receiver is receiving electrical signals from the antenna via the fixed electrical connection, the transmitter can be controlled to not transmit any signal to the fixed electrical connection.
Such an arrangement works for a communication protocol that allows transmission and reception of communication data over a common signal path at different times, such as time-division multiplexing. However, such an arrangement can expose the receiver to the electrical signals transmitted by the transmitter, which can have undesirable consequences. For example, the transmitter may be designed to transmit signals of relatively large voltage swing. The voltage swing can be designed to cover for attenuation of transmitted signal power, as the signal propagates within the space. The voltage level of the transmitted signal may cause high voltage stress to the transistor devices of the receiver, which can lead to device breakdown. As a result, the reliability of the receiver can be degraded.
Instead of a fixed electrical connection, a transmitter/receiver (T/R) switch can be provided to allow one of transmitter or the receiver to be electrically connected to the antenna. The T/R switch can include a first transistor that controls the electrical connection between the antenna and the transmitter, and a second transistor that controls the electrical connection between the antenna and the receiver. The two transistors can be controlled to operate in tandem. When the transmitter transmits electrical signals to the antenna via the first switch, the receiver can be electrically isolated from the antenna by the second switch. When receiving electrical signals from the antenna via the second switch, the transmitter can be electrically isolated from the antenna by the first switch. The T/R switch is typically also an off-chip component.